As liquid crystal display devices, active matrix liquid crystal display devices in which pixels include switch elements are widely used. As illustrated in FIG. 13, a pixel 5000 includes a transistor 5001 which functions as a switch element, a liquid crystal element 5002 to which a video signal is input from a wiring 5004 through the transistor 5001, and a capacitor element 5003 which holds the video signal written to the liquid crystal element 5002. With provision of the capacitor element 5003, a video signal can be held even when the switch element is off.
Silicon, which has broad utility, is used as the semiconductor material of a transistor. However, in recent years, not only broad utility but also improvement in performance has been expected, and a technique related to a field effect transistor (also referred to as FET) including an oxide semiconductor has attracted attention (see Reference 1).
Further, in order to reduce the response time of a liquid crystal, a technique for instantaneously applying high voltage to the liquid crystal before a video signal is written (i.e., overdrive) has been performed (see Reference 2).